This invention relates to keypads such as are employed in telephones and, more particularly, to a keypad employing a flexible conductive diaphragm disposed between insulating buttons of the keypad and contacts of a printed circuit board.
Keypads, such as telephone keypads, are constructed with twelve keys or push buttons arranged in an array of three columns by four rows. The keypads are manufactured in large numbers and, therefore, a form of construction which permits manufacturing simplicity and economy is desirable. In order to attain this goal, various forms of telephone keypads are currently manufactured. In one form of construction, the buttons press contacts against terminals on a printed circuit board, components of the keypad being manufactured by processes of plastic molding. Other forms of construction include a metal diaphragm over a printed circuit board, and a flexible circuit on plastic film with coined domes. However, these keypads are not as simple and economical to manufacture as would be desirable.
One example of interest in the prior construction of keypads is found in a telephone keypad comprising an insulating elastomeric diaphragm having conductive rubber disks affixed thereto to serve as contacts for connecting terminals on a printed circuit board. Upon advancement of a button being pushed by a user of the telephone, the diaphragm deforms and one of the conductive disks is urged into contact with terminals on the printed circuit board to complete a circuit on the board. However, this form of keypad is disadvantageous in that the manufacturing process requires the emplacement of numerous disks at their respective locations on the insulating diaphragm.